Mobile data and voice communication continues to grow with an increasing demand for higher data transmission performance, for example for high definition video transmissions or gaming applications. Additionally, the increasing popularity of data and voice communication requires that communication needs of a large number of users must be met, even in situations in which a large number of users are located within a small area, for example in sports arenas, shopping malls or large office buildings.
In order to increase data transmission performance and reliability, the so-called multiple-input and multiple-output (MIMO) technology may be used in a wireless radio telecommunication system for transmitting information between a base station and a terminal, for example mobile devices like mobile telephones, mobile computers and tablet computers and stationary devices like personal computers or cash registers.
MIMO systems may use multiple send and receive antennas for wireless communication at the base station as well as at the terminal. The MIMO technology forms the basis for coding techniques which use the temporal as well as the spatial dimension for transmitting information. The enhanced coding provided in MIMO systems allows a spectral and energy efficiency of the wireless communication to be increased.
The spatial dimension may be used by spatial multiplexing. Spatial multiplexing is a transmission technique in MIMO wireless communication to transmit independent and separately encoded data signals, so-called streams, from each of the multiple transmit antennas. Therefore, the spatial dimension is reused, or multiplexed, more than one time.
Additionally or as an alternative, a frequency of the radio signals for the transmission may be increased. The transmission may be based on radio signals with higher frequencies or shorter wavelengths, for example a radio signal with a frequency of several gigahertz or a wavelength of only a few millimetres may be used. When operating at higher frequencies or shorter wavelengths, the aperture of an antenna becomes small. In electromagnetics and antenna theory, antenna aperture or effective area is a measure of how effective an antenna is at receiving the power of radio waves. This may decrease transmission efficiency. For mitigating this, multiple antennas may be used. However, this may raise the problem how to combine the signals from the multiple antennas for best performance.